Aldoses analysis

The structural determination of those bicyclic compounds remained under discussion for some time, until Wickstrom et al.44 could (1) confirm the formation of fused bicyclic OZT-sugars and, more important (2) ascertain the furan forms for aldoses and the pyran form for D-fructose (Scheme 21). Those results were later confirmed by Jochims et al. through the first NMR analysis performed on OZTs.45... 

Yoshikawa M, Nishida N, Shimoda H, Takada M, Kawahara Y, Matsuda H. (2001) Polyphenol constituents from Salacia Species Quantitative analysis of mangiferin with a-glucosidase and aldose reductase inhibitory activities. Yakugaku Zasshi 121 371-378. 

The chemistry of the 2,5-anhydrides of aldoses subsequently entered a prolonged lull, and Peat s review21 of 1946 in this Series does not report on any work later than 1925. The experimental basis of the deamination of amino sugars with nitrous acid was, nevertheless, established. The progress afterwards made in the conformational analysis of sugars made it possible for Shafizadeh22 to draw a parallel with the nitrous acid deamination of the aminocyclohexanols, and to rationalize the whole of these results. 

Three aldose reductase inhibitors (490 492) were isolated from Dictyodendrilla sp. from Japan and their structures were determined by X-ray analysis and spectroscopic studies [418],... 

Fortunately, the rules of chemical reactivity and conformational analysis, coupled with the laws of thermodynamics, join forces to allow us to functionalize polyhydroxy aldehydes and ketones (aldoses and alduloses) in a selective and predictable fashion. 

Several reviews have already been published on the subject, for example, the acetala-tion of alditols [4], of aldoses and aldosides [5,6], and of ketoses [7]. Some aspects of the stereochemistry of cyclic acetals have been discussed in a review dealing with cyclic derivatives of carbohydrates [8], also in a general article [9] and, more recently, in a chapter of a monograph devoted to the stereochemistry and the conformational analysis of sugars [10], Aspects on predicting reactions patterns of alditol-aldehyde reactions are reviewed within a general series of books on carbohydrates [11]. The formation and migration of cyclic acetals of carbohydrates have also been reviewed [12,13],... 

Hinton, C. L. and Macara, T. 1927. The determination of aldose sugars by means of chloramine-T, with special reference to the analysis of milk products. Analyst 52, 668-688. 

Scheme 2. Mechanistic analysis of reaction pathways for NeuA catalysis that considers the crucial influences of C-3 and anomeric configurations and of chair conformations on the three-point attachment of aldoses as acceptor substrates, Si-face attack leads to regular (4S)-configurated adducts while re-face attack leads to inverted stereochemistry (abbreviations anm = anomerization, inv = ring inversion)...

It is well known that the Maillard reaction in foods is initiated by the formation of colorless and tasteless intermediates, which preferentially are formed in low-moisture systems ( ,5.). In this way by reaction of glucose with amino acids fructose-amino acids are formed via Amadori rearrangement of the primary glucosyl-ami-no acids (1 ). Fructose-amino acids e.g. have been isolated from freeze-dried apricots and peaches ( 6,7,8j. Amadori compounds arising from aldoses and amino acids are formed during drying of foods of plant origin and can be easily detected by amino acid analysis (j>). 

Quantitative Analysis of Mixtures of Sugars by the Method of Partition Chromatography. Part II. The Separation and Determination of Methylated Aldoses, E. L. Hirst, L. Hough, and J. K. N. Jones,/. Chem. Soc., (1949) 928-933. 

Aldonitrile acetates of sugars have been applied to their GC analysis in different polysaccharides [442] on LAC-4R-886 polyester stationary phase (190°C)and to the analysis of polyols and aldoses in urine and crystalline lenses [444] on a capillary column of borosilicate glass (60 m X0.3 mm l.D.) coated with SE-30 containing a dispersion of Silanox 101 (temperature programming at l°C/min from 150°C). These derivatives were very stable and a uniform product was formed from every individual substrate. 

Trifluoroacetates have been applied to the analysis of sugars in the same way as acetates. Imanari et al. [445] analysed aldoses after a prior reduction, as follows. A 0.5-ml volume of 1% NaBH4 in water was added to 0.5 ml of an aqueous solution containing 100-500 pg of a mixture of aldoses. The solution was allowed to stand at room temperature for 30 min and the excess of borohydride was decomposed by adding 0.5 ml of Amberlite CG-120 (H+). The resin was removed by filtration and the filtrate was evaporated to dryness. Borate was removed by the three-fold addition of 1 ml of methanol and subsequent evaporation. The residue was vacuum dried and dissolved in 0.1 ml of ethyl acetate and 0.1 ml of TFA anhydride. After 30 min at room temperature, 1—2 pi were taken for analysis. The resulting derivatives were more volatile than acetates and provided symmetric peaks on a column packed with 2% of XE-1105 (see Fig. 5.30). 

Most imidazoline, imidazolone, and imidazole derivatives are stable ring structures and usually exist only in the cyclic forms. For example, in the reaction of methyl 2-deoxy-2-isothiocyanato-a-D-glucopyranoside 149 with D-glucosamine 148, a-deoxy-2-(3-substituted thioureido)-D-aldose, 150, is presumably the reaction intermediate. However, the ring-chain tautomeric equilibrium of 150 shifts towards the cyclic form to yield 151 which is the only detectable form by NMR analysis (Scheme 41) <1999TA3011>. 

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